It is known that the image dyes in color photographs are liable to fade as a result of the presence of fungi, in addition to the usual fading effects due to heat and light. Photographic photosensitive materials are often stored by being adhered or sandwiched in an album made from paper or on a mounting board, or by being sandwiched on Japanese paper with a mounting board on the surface. However, when photographs are finished for storage in this way the paste used for adhesion and the paper fibers themselves provide nutrient sources. Fungi grow and proliferate, especially under conditions of high temperature and humidity, and problems arise with fading of the image dyes, especially the cyan dyes, as a result of the action of products excreted by the fungi.
The fungi themselves can be wiped off the photograph, but the fading cannot be restored in this way and the quality of the image is permanently degraded. This is a serious problem.
Attempts have been made in the past to overcome this problem by using fungicides (biocides). There are very many fungicides that have been used successfully in many applications, and they could be used with silver halides. However, none has been found which has the desired fungicidal effect without having an adverse effect on various photographic characteristics, or being toxic to humans.
Known fungicides include those disclosed, for example, in U.S. Pat. Nos. 2,226,183, 2,762,708, 2,897,081, 3,185,571, 2,663,639, 3,503,746, 3,342,810 and 3,778,276, British Patents 987,010 and 1,065,920, and JP-A-57-157244 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application").
However, virtually all of these fungicides are organic fungicides and they may be expensive, or liable to oxidization or sublimation. They have the disadvantage that their effect during the storage of photographic photosensitive materials is poorly retained.
It has been indicated in JP-A-61-233743 that a fungicidal effect can be obtained with little staining and without the occurrence of photostaining by using combinations of specified fungicides and pyrazoloazole based magenta couplers.
It has also been proposed that fungi are not likely to grow if the photosensitive material is made acidic after processing, but such a procedure gives rise to the following problems in practice.
(1) Use of known organic acids (for example, citric or acetic acids) has the opposite effect and provides nutrients for fungi, thus promoting the growth of fungi and increasing the fading. PA1 (2) On acidification to such an extent that fungal growth does not occur, dye fading is liable to occur as a result of the effect of the acid, and the overall storage properties of the image are worsened. This effect is especially pronounced when inorganic acids are used.
On the basis of the facts outlined above, it has been indicated in JP-A-60-135942, corresponding to EP 147016 A2, that the problem can be overcome by lowering the pH of the photosensitive material by immersing the material in an aqueous solution of an ammonium salt (for example, ammonium sulfate) after processing and releasing the ammonium ion from the photosensitive material as ammonia.
However, although good results can be obtained in this way, the situation is the same as that described earlier once the ammonia has been liberated and dispersed, and this method does not provide a real solution to the problem.
A technique is desired by which the fading due to action of material excreted by fungi can be prevented even when fungi are present.
It has been proposed that a cyan coupler, high boiling organic solvent and water-insoluble and organic solvent-soluble polymer are disclosed in WO 88/00723, EP 280238 and JP-A-63-104050, etc.